This is a great example of how a historical/literary/cultural/geographical reference is picked up by another cultural sphere and takes on a life of its own.
La ligne Maginot, as the Encyclopedia Britannica states, is an:
elaborate defensive barrier in northeast France constructed in the 1930s and named after its principal creator, André Maginot, who was France’s minister of war in 1929–31.
According to Naver's edition of the 고려대 한국어대사전 (Korea University Korean Dictionary), the meaning of the Korean expression 마지노선 is (bold mine, not original):
어떤 일이나 사안에 대하여 받아들이거나 인정할 수 있는 최저의 한계선을 비유적으로 이르는 말.
... that is to say, the final line being the lowest acceptable standard. Although it is an educated "reference", I'd say it's in fairly common use, and I'd surmise that it's because it sounds similar to 마지막 선 (a literal final line) in Korean.
In the media of modern France, though, it is not really used this way to refer to standards (someone from French StackExchange may correct me here!); instead, it is thought of as a reference for an obsolete barrier or distinction. For example, an article from Le Monde published in 2017:
Elle n’empêcha pas l’avancée des troupes allemandes, mobiles et rapides, en 1940. Témoignage pétrifié, vestige d’une fausse bonne idée, la ligne Maginot se visite.
Le clivage droite-gauche est-il aussi obsolète que le fut cette fortification hérissée de tourelles, de barbelés et de casemates ?